[net-next,PATCH v2] enetc: Increase eMDIO MDC rate to 2.5 MHz

[Marek Vasut <marex@nabladev.com>]

The current eMDIO MDC rate is 558 kHz on i.MX95 B0. This is very low,
but also very compatible. However, for example NXP TJA1120 PHY needs
at minimum 1 MHz MDC clock and 558 kHz does not work with that PHY.

As a minimum change, increase the MDC clock to 2.5 MHz which matches
the 802.3 specification. Also, even old PHYs like LAN8210Ai, KSZ8794,
DP83822 support up to 2.5 MHz MDC clock frequency, and it covers the
NXP TJA1120 as well. There is no known rationale for why the 558 kHz
was picked when the eMDIO driver was added.

Signed-off-by: Marek Vasut <marex@nabladev.com>
---
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Andrew Lunn <andrew+netdev@lunn.ch>
Cc: Clark Wang <xiaoning.wang@nxp.com>
Cc: Claudiu Manoil <claudiu.manoil@nxp.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Vladimir Oltean <vladimir.oltean@nxp.com>
Cc: Wei Fang <wei.fang@nxp.com>
Cc: imx@lists.linux.dev
Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
---
V2: Use 2.5 MHz per 802.3 spec, update commit message
---
 drivers/net/ethernet/freescale/enetc/enetc_mdio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/freescale/enetc/enetc_mdio.c b/drivers/net/ethernet/freescale/enetc/enetc_mdio.c
index 998aaa394e9c4..a90a04a47befd 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc_mdio.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc_mdio.c
@@ -24,7 +24,7 @@
 
 #define ENETC_EMDIO_CFG \
 	(MDIO_CFG_HOLD(2) | \
-	 MDIO_CFG_CLKDIV(258) | \
+	 MDIO_CFG_CLKDIV(66) | \
 	 MDIO_CFG_NEG)
 
 #define MDIO_CTL_DEV_ADDR(x)	((x) & 0x1f)
-- 
2.53.0